Li Zhaojun, Hou Liangtao, Ran Lingling, Kang Jing, Yang Jiuru
College of Electronics Engineering, Heilongjiang University, Harbin 150080, China.
Key lab of Electronics Engineering, College of Heilongjiang Province, Heilongjiang University, Harbin 150080, China.
Sensors (Basel). 2019 Sep 4;19(18):3820. doi: 10.3390/s19183820.
In this paper, a novel in-line modal interferometer for refractive index (RI) sensing is proposed and experimentally fabricated by cascading single-taper and multimode-double- cladding-multimode (MDM) fiber structure. Owing to evanescent field in taper area, the ultra-sensitive and linear intensity-responses to the varied surrounding RI are gained in both single- and double-pass structures. Moreover, the crosstalk from temperature can be effectively discriminated and compensated by means of the RI-free nature of MDM. The experimental results show that the RI sensitivities in single- and double-pass structures, respectively, reach 516.02 and 965.46 dB/RIU (RIU: refractive index unit), both with the slight wavelength shift (0.2 nm). The temperature responses with respect to wavelength and intensity are 68.9 pm°C/0.103 dB°C (single-pass structure) and 103 pm°C/0.082 dB·°C (double-pass structure). So the calculated cross-sensitivity of intensity is constrained within 8.49 × 10 RIU/°C. In addition, our sensor presents high measurement-stability (0.99) and low repeatability error (<4.8‱). On account of the ~620 μm size of taper, this compact sensor is cost-efficient, easy to fabricate, and very promising for the applications of biochemistry and biomedicine.
本文提出了一种用于折射率（RI）传感的新型在线模态干涉仪，并通过级联单锥和多模双包层多模（MDM）光纤结构进行了实验制作。由于锥形区域的倏逝场，在单通道和双通道结构中均获得了对周围变化的RI的超灵敏和线性强度响应。此外，借助MDM的无RI特性，可以有效区分和补偿来自温度的串扰。实验结果表明，单通道和双通道结构中的RI灵敏度分别达到516.02和965.46 dB/RIU（RIU：折射率单位），且波长偏移均较小（约0.2 nm）。波长和强度的温度响应分别为68.9 pm/°C/0.103 dB/°C（单通道结构）和103 pm/°C/0.082 dB·°C（双通道结构）。因此，计算得出的强度交叉灵敏度限制在8.49×10 RIU/°C以内。此外，我们的传感器具有高测量稳定性（约0.99）和低重复性误差（<4.8‱）。由于锥形尺寸约为620μm，这种紧凑型传感器成本效益高，易于制造，在生物化学和生物医学应用中非常有前景。
